186 MEMOIRS OF THE UNIVERSITY OF CALIFORNIA 



0.33 and 0.36 of the total Ipiigth of the body. The sulcus begins at the apex and extends poster- 

 iorly in an ahuost straight line to near the antapex. It lies in a rather wide shallow trough 

 with rounded sides which fade out in the apical regions. The anterior flagellar pore is slightly 

 below the proximal junction of the girdle and sulcus. The posterior pore opens at about 0.58 

 of the distance between the anterior pore and the antapex. 



The nucleus is spherical and located in the posterior third of the body. Its axis is about 

 0.27 transdiameter in length. A long sacklike pusnle opens into the anterior flagellar pore. 

 The cytoplasm is clear and finely granular, and filled with metabolic products, evidences of 

 holozoic nutrition. In the central part of the body was a large, brownish food mass, obscured 

 by a great mass of dark, refractive granules. Radiating out from this were long slender blue 

 green rodlets, or radial canals. Smaller groups of granules filled the remaining central and 

 anterior regions of the body, with a few small bodies, yellow ochre in color. In the antapical 

 region were several large vacuoles filled with fluid, colored salmon pink like the pusule. 



This species, like G. dogicli, has a distinct ectoplasmic region, composed of a thin layer 

 surmounted by an alveolar layer, the outer portions of the alveoli being rounded and giving a 

 roughened appearance to the surface of the body. This layer is appreciably thicker in the 

 antapical region and is a striking feature of the body in a general view. The color of the 

 organism is pale turquoise gi'een shading to deep yellow on the right side of the hypocone, and 

 slightly diffused throughout the cytoplasm, hut with a greater concentration in the peripheral 

 region. The surface exhibited no striae or other markings. 



DiMEXsioxs. — Length, 15^ ; transdiameter, 95/^ ; axis of nitelens, 27^*. 



OccuREExCE. — A single individual was taken on August 13, 1917, with a 

 No. 25 silk net, 0.75 of a mile off La Jolla, California, in a haul from 80 meters 

 to the surface and in a surface temperature of 21 ^9 C. 



CoisiPAEisoxs. — This is one of the most highly differentiated species of 

 Gymnodiuium, as shown in its highly developed ectoplasm, and belongs with 

 the subgenus Paclujdinium. In its cytoplasmic structure, coloring, and size it 

 stands very close to G. dogieli and G. pacliijdermatnm (fig. AA, 8, 5), but differs 

 greatly from them in its relative proportions and arrangement of girdle, having 

 the shortest epitheea of the three and an anterior sulcal notch. 



Gymnodinium attenuatum sp. nov. 



Text figure Y, 12 



Diagnosis. — A small species with ovate fusiform body, apices acute, com- 

 pressed laterally, its length 2.24 transdiameters ; girdle premedian, displaced 

 less than its own width ; sulcus extending from apex to near antapex ; surface 

 finely striate. Length, 65/^. Pacific off La Jolla, California, June, July. 



Description. — This is a small species ^nth ovate body sharply pointed at both ends, and 

 compressed laterally, its dorsoventral diameter equaling 1.17 transdiameters and its length 2.24 

 transdiameters. It is slightly asymmetrical with the ventral face having a greater convexity 

 than the dorsal face. The epicone is nearly 0.5 shorter in length than the hypocone. The 

 basal portion of the epicone is rotund, tapering anteriorly to a sharp, slender point. The apex 

 is somewhat excentric, being thrown dorsad by the greater slope of the ventral face. Its length 

 is about 0.3 of the total length of the body. The length of the hypocone is about 0.66 of the 

 total length of the body. It is rounded anteriorly and tapers to a long, slender antapex. 



